He broke off with a gasp of astonishment as the whole building suddenly began to shake. "Good grief!" Bud exclaimed. "This isn't part of your testing routine, is it?" His question was drowned out by cries of alarm and the sound of cracking glass. The walls and roof were shuddering and creaking, and the concrete floor was heaving under their feet. [Illustration (earthquake in the lab)] "Look out! The test stand's breaking loose!" Tom warned. Mr. Faber and two of his men tried frantically to brace the heavy test stand which held the telemetering device. Another engineer rushed toward the door to see what was happening outside. Before he reached it, another shock knocked all of them off their feet. Electronic equipment cascaded from the wall shelves, and a heavy-duty chain hoist came loose from its overhead track, plunging to the floor with a terrifying crash. "An earthquake!" Tom gasped. Bud, meanwhile, clawed a handhold on a wire screen enclosing an air compressor and pulled himself to his feet. But the next moment a third, more violent tremor rocked the building, knocking him over. "The roof! It's caving in!" he heard someone scream. As his eyes flashed upward in panic, Bud caught a brief glimpse of the ponderous test stand with the priceless telemeter tilting to one side. An instant later it crashed over, pinning Mark Faber beneath it! Bud threw up his arms to protect himself, but too late! A falling beam caught him on the back of the head and the young flier blacked out. For minutes, no one stirred among the wreckage. Then Tom, who had been stunned by some falling debris, raised himself to a sitting position. "Good night!" Tom's eyes focused in horror on the wreckage enveloped by still-billowing dust. The sky was visible through several gaping holes in the roof, which was sagging dangerously on its supporting trusses. Only two thirds of the walls were still standing. Suddenly Tom stiffened in fear. "Bud!" The young inventor had just noticed his friend lying pinned beneath a heavy beam nearby. _Was he still breathing?_ Disregarding his own injuries, Tom hastily freed himself from the debris and groped his way to Bud's side. With a desperate heave, he shoved the beam away, then cradled Bud's head in his arm. His friend's eyelids flickered. "Are you all right?" Tom asked fearfully. The answer came in a groan. "O-oh!... Wow!... What hit me?" "You got conked by a falling timber. Or grazed, at least," Tom added thankfully. "If that beam had landed square on your noggin, even a rock-head like you couldn't have survived!" Bud managed to grin. "We grow 'em tough out in California where I come from!" he joked. Somewhat shakily, Bud got to his feet with Tom's assistance. Both boys were heartsick as they surveyed the damaged laboratory, wondering where to begin rescue operations.